We investigate the effect of high school racial composition, measured as percent of non-Hispanic white students, on trajectories of depressive symptoms from adolescence to early adulthood. We also explore whether the effect of school racial composition varies by respondent race/ethnicity and whether adult socioeconomic status mediates this relationship. We analyzed four waves of data from the National Longitudinal Study of Adolescent Health using 3-level linear growth models. We restricted our sample to respondents enrolled in grades 9-12 in 1994/5 who were interviewed at a minimum in Waves I and IV. This resulted in 10,350 respondents enrolled in 80 high schools in 1994/5 (5,561 whites, 2,030 blacks, 1,834 Hispanics, 738 Asians, and 187 of other race). As the percentage of white students increased at the high school respondents attended in 1994/5, blacks reported more depressive symptoms. This effect did not vary by age. In comparison, Asian and Hispanic respondents who attended predominantly white high schools had lower levels of depressive symptoms than their counterparts who attended predominantly minority schools, but they also experienced a slower decline in depressive symptoms through early adulthood. Adult SES mediated the relationship between high school racial composition and depressive symptoms for black, but not for Asian or Hispanic respondents. Our results suggest that high school racial composition is associated with trajectories of depressive symptoms through early adulthood, but the effect differs by respondents' race/ethnicity. Racial/ethnic disparities in depressive symptoms during early adulthood may have their origins in adolescence.